For a MPEG-2 to MPEG-2 transcoder, the decoded information, such as code modes and motion vectors (MVs), are often re-used in re-encoding in order to speed the processing. However, for a MPEG-2 to MPEG-4 (Also referred to as Advanced Video Coding (AVC), MPEG-4 part 10 or H.264) transcoder, the decoded MPEG-2 information, such as code modes and MVs, cannot be directly re-used in MPEG-4 encoder because MPEG-2 and MPEG-4 are two different standards. For example, MPEG-2 standard supports two partition sizes, 16×16 for frame block and 8×16 for field block. On the other hand, MPEG-4 supports four macroblock (MB) level partitions of 16×16, 16×8, 8×16 and 8×8, and four sub-MB level partitions of 8×8, 8×4, 4×8 and 4×4 in both frame and field. Thus, the partition sizes between MPEG-2 and MPEG-4 are typically not compatible.
As a result of the differences between code modes, MVs and other differences between MPEG-2 and MPEG-4, in order to view information encoded in an MPEG-2 stream in an MPEG-4 format, a transcoder is required to fully decode from MPEG-2 to baseband and then fully re-encode from baseband to MPEG-4. The current MPEG-2 to MPEG-4 transcoder is equivalent to a full MPEG-2 decoder followed by a full MPEG-4 encoder. The current process therefore requires significant processing resources because MPEG-4 is a complicated standard and is costly to fully encode.